U.S. Pat. No. 4,768,347 assigned to the assignee hereof discloses a refrigerant recovery system that includes a compressor having an inlet coupled through an evaporator and through a solenoid valve to refrigeration equipment from which refrigerant is to be withdrawn, and an outlet coupled through a condenser to a refrigerant storage container or tank. The refrigerant storage container is carried by a scale having a limit switch coupled to control electronics to prevent or terminate further refrigerant recovery when the container is full. The scale comprises a platform pivotally mounted by a hinge pin to a wheel cart, which also carries the evaporator/condenser unit, compressor, control electronics, and associated valves and hoses.
U.S. Pat. No. 4,805,416, also assigned to the assignee hereof, discloses systems for recovering, purifying and recharging refrigerant in which, during a purification cycle, refrigerant is circulated from a refrigerant storage container in a closed path through a circulation valve and a filter for removing water and other contaminants, and then returned to the container. U.S. Pat. No. 4,939,905, also assigned to the assignee hereof, discloses a refrigerant handling system that includes a multiple-section condenser, and means responsive to refrigerant temperature and pressure at the outlet of the evaporator for automatically and selectively controlling flow of refrigerant from the compressor outlet to the individual condenser sections. This construction permits use of the disclosed system in connection with differing types of refrigerants, such as R12, R22 and R502, without contamination of the refrigerants due to intermixing with refrigerant retained in the condenser.
A problem with refrigerant handling systems of the types discussed above involves clearing system components of refrigerant when it is desired to employ the system with a differing type of refrigerant, or when it is desired to perform routine maintenance or repair on the system components. Components upstream of the compressor inlet can be efficiently cleared by operation of the compressor. However, components downstream of the compressor outlet, such as a condenser or refrigerant filter, retain refrigerant in liquid phase. The multiple-section condenser disclosed in above-noted U.S. Pat. No. 4,939,905 permits operation with differing types of refrigerants. However, it involves the expense of a multiple-sectioned condenser, and is not as readily amenable as desired to retrofit in recovery equipment currently in the field. Furthermore, refrigerant in the condenser sections would be lost to the atmosphere in the event that the condenser is disconnected for repair or other purposes. Likewise, it is important to provide facility for removing refrigerant from a refrigerant filter and associated piping to minimize release of refrigerant to the atmosphere when the filter cartridge must be changed, an operation that must be performed fairly frequently.